Phosphorylation of serine 10 in histone H3 is functionally linked in vitroand in vivo to Gcn5-mediated acetylation at lysine 14

Multiple covalent modifications exist in the amino-terminal tails of core h istones, but whether a relationship exists between them is unknown. We exam ined the relationship between serine 10 phosphorylation and lysine 14 acety lation in histone H3 and have found that, in vitro, several HAT enzymes dis played increased activity on H3 peptides bearing phospho-Ser-10. This augme nting effect of Ser-10 phosphorylation on acetylation by yGcn5 was lost by substitution of alanine for arginine 164 [Gcn5(R164A)], a residue close to Ser-10 in the structure of the ternary tGcn5/CoA/histone H3 complex. Gcn5(R 164A) had reduced activity in vivo at a subset of Gcn5-dependent promoters, and, strikingly, transcription of this same subset of genes was also impai red by substitution of serine 10 to alanine in the histone H3 tail. These o bservations suggest that transcriptional regulation occurs by multiple mech anistically linked covalent modifications of histones.